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	<head>
		<title>three.js webgl - materials - HDR texture</title>
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			body {
				color: #fff;
				font-family:Monospace;
				font-size:13px;
				text-align:center;
				font-weight: bold;

				background-color: #000;
				margin: 0px;
				overflow: hidden;
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			#info {
				color:#fff;
				position: absolute;
				top: 0px; width: 100%;
				padding: 5px;

			}

			a { color: red; }

		</style>
	</head>
	<body>

		<div id="container"></div>
		<div id="info">
			<a href="http://threejs.org" target="_blank" rel="noopener">three.js</a> - webgl HDR texture example -
			based on <a href="http://spidergl.org/example.php?id=13" target="_blank" rel="noopener">SpiderGL</a>
		</div>

		<script src="../build/three.js"></script>

		<script src="js/WebGL.js"></script>
		<script src="js/libs/stats.min.js"></script>

		<!-- HDR fragment shader -->

		<script id="fs-hdr" type="x-shader/x-fragment">

			uniform sampler2D   tDiffuse;
			uniform float       exposure;
			uniform float       brightMax;

			varying vec2  vUv;

			vec3 decode_pnghdr( const in vec4 color ) {

				// remove gamma correction
				vec4 res = color * color;

				// decoded RI
				float ri = pow( 2.0, res.w * 32.0 - 16.0 );

				// decoded HDR pixel
				res.xyz = res.xyz * ri;
				return res.xyz;

			}

			void main()	{

				vec4 color = texture2D( tDiffuse, vUv );
				color.xyz  = decode_pnghdr( color );

				// apply gamma correction and exposure
				//gl_FragColor = vec4( pow( exposure * color.xyz, vec3( 0.474 ) ), 1.0 );

				// Perform tone-mapping
				float Y = dot(vec4(0.30, 0.59, 0.11, 0.0), color);
				float YD = exposure * (exposure/brightMax + 1.0) / (exposure + 1.0);
				color *= YD;

				gl_FragColor = vec4( color.xyz, 1.0 );

			}

		</script>

		<!-- HDR vertex shader -->

		<script id="vs-hdr" type="x-shader/x-vertex">

			varying vec2 vUv;

			void main()	{

				vUv  = uv;
				gl_Position = projectionMatrix * modelViewMatrix * vec4( position, 1.0 );

			}

		</script>


		<script>

			if ( WEBGL.isWebGLAvailable() === false ) {

				document.body.appendChild( WEBGL.getWebGLErrorMessage() );

			}

			var container, stats;

			var camera, scene, renderer;
			var materialHDR, quad;

			var sign = 1, rate = 1;

			var clock = new THREE.Clock();

			init();
			animate();

			function init() {

				container = document.getElementById( 'container' );

				camera = new THREE.PerspectiveCamera( 50, window.innerWidth / window.innerHeight, 1, 10000 );
				camera.position.z = 900;

				scene = new THREE.Scene();

				var texture = new THREE.TextureLoader().load( "textures/memorial.png" );
				texture.minFilter = THREE.LinearFilter;
				texture.magFilter = THREE.NearestFilter;

				materialHDR = new THREE.ShaderMaterial( {

					uniforms: {
						"tDiffuse": { value: texture },
						"exposure": { value: 0.125 },
						"brightMax": { value: 0.5 }
					},
					vertexShader: getText( 'vs-hdr' ),
					fragmentShader: getText( 'fs-hdr' )

				} );

				var plane = new THREE.PlaneBufferGeometry( 512, 768 );

				quad = new THREE.Mesh( plane, materialHDR );
				quad.position.z = - 100;
				scene.add( quad );

				renderer = new THREE.WebGLRenderer();
				renderer.setPixelRatio( window.devicePixelRatio );
				renderer.setSize( window.innerWidth, window.innerHeight );
				container.appendChild( renderer.domElement );

				stats = new Stats();
				container.appendChild( stats.dom );

				//

				window.addEventListener( 'resize', onWindowResize, false );

			}

			function onWindowResize() {

				camera.aspect = window.innerWidth / window.innerHeight;
				camera.updateProjectionMatrix();

				renderer.setSize( window.innerWidth, window.innerHeight );

			}

			function getText( id ) {

				return document.getElementById( id ).textContent;

			}

			//

			function animate() {

				requestAnimationFrame( animate );

				render();
				stats.update();

			}

			function render() {

				var delta = clock.getDelta() * 5;

				if ( materialHDR.uniforms[ "exposure" ].value > 0 || materialHDR.uniforms[ "exposure" ].value < 1 ) {

					rate = 0.25;

				} else {

					rate = 1;

				}

				if ( materialHDR.uniforms[ "exposure" ].value > 5 || materialHDR.uniforms[ "exposure" ].value <= 0 ) {

					sign *= - 1;

				}

				materialHDR.uniforms[ "exposure" ].value += sign * rate * delta;

				renderer.render( scene, camera );

			}

		</script>
	</body>
</html>
